Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

our surroundings. With the help of these fundamental dimensions, we can then define or derive

engineering variables that are commonly used in analysis and design. As you will see in the fol-

lowing chapters, there are many engineering design variables that are related to these funda-

mental dimensions (quantities). As we also discussed and emphasized previously, we need not

only physical dimensions to describe our surroundings, but also some way to scale or divide

these physical dimensions. For example, time is considered a physical dimension, but it can be

divided into both small and large portions (such as seconds, minutes, hours, and so on). To

become a successful engineer, you must first fully understand these fundamentals. Then it is

important for you to know how these variables are measured, approximated, calculated, or used

in engineering analysis and design. A summary of fundamental dimensions and their relation-

ship to engineering variables is given in Table 6.7. After you understand these concepts, we will

explain the concepts of energy and power in Chapter 13. Study this table carefully.

152 Chapter 6 Fundamental Dimensions and Units

TABLE 6.7 Fundamental Dimensions and How They Are Used in Defining Variables that Are Used in Engineering Analysis and Design

Fundamental

Dimension Related Engineering Variables

Length (L) Radian , Area (L

2

) Volume (L

3

) Area moment

[Chapter 7] Strain of inertia (L

4

)

Time (t) Angular speed ,

[Chapter 8] Angular acceleration Volume flow rate

Linear speed ,

Linear acceleration

Mass (M) Mass flow rate , Density ,

[Chapter 9] Momentum Specific volume

Kinetic energy

Force (F) Moment (LF), Pressure ,

[Chapter 10] Work, energy (FL), Stress ,

Linear impulse (Ft), Modulus of Specific weight ,

Power elasticity ,

Modulus of

rigidity

Temperature (T) Linear thermal expansion Volume thermal

[Chapter 11] expansion

Specific heat

Electric Current (I) Charge (It) Current density

[Chapter 12]^1

I

L^2

2

1

FL

MT^2

1

L^3

(^1) L^3 T 2
L
LT^2 ,
1
F
L^22
1
F
(^1) L 22
FL
t^2
1
F
L^32
1
F
L^22
1
F
L^22
1
ML^2
t^22
1
L^3
(^1) M 2
ML
t^2
1
M
(^1) L 32
M
t^2
1
L
t^22
1
L
t^2
1
L^3
(^1) t 2
1
t^22
1
1
t^2
1
L
L^2
1
L
L^2
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